Chemical composition and insecticidal activity of two Eucalyptus essential oils against the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae)

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann), is the single most important pest species affecting fresh fruit particularly citrus varieties. Over time, pest control approaches have been chronologically associated with procedures more and more friendly to the environment, starting with the use of insecticides, then sterile insecticides and finally plant essential oils as natural sources of pesticides. Essential oils (EO) extracted from leaves of Eucalyptus campaspe (Spencer Moore) and E. torquata Luehm were tested for their toxicity and repellency against C. capitata medflies. The EOs yields were 3.36% for E. campaspe and 1.83% for E. torquata. The main constituents in E. campaspe EO were 1,8-cineole (34.1%), beta-eudesmol (10.4%) and globulol (9.7%), while the major components of E. torquata EO were globulol (42.7%), germacrene B (11.2%), beta-eudesmol (6.7%) and viridiflorol (5.3%). In different trials E. campaspe EO showed higher toxic and repellent activities against C. capitata adults than E. torquata L EO. The EO of E. campaspe used as fumigant displayed a much more pronounced repellent and toxic effect on C. capitata than its formulation in ingestion or contact bioassays. While the EO of E. torquata had moderate insecticidal activities, E. campaspe EO has a higher inhibitory effect than that of E. torquata on acetylcholinesterase activity. The EOs of E. torquata and E. campaspe appeared to contain components that could serve as a basis for the synthesis of derivatives or analogs useful as pest control agents.